Blast furnaces have been configured such that pig iron can be produced from iron ore by charging iron ore, calcium oxide and coke starting materials from the top to the interior of the blast-furnace body and injecting in hot wind and blast-furnace injecting pulverized coal as an auxiliary fuel from a tuyere on the bottom side of the side part of the blast-furnace body.
In order to stably operate the above blast furnaces, it is necessary to suppress adhesion of the blast-furnace-injecting-coal ash or blockages caused by the blast-furnace-injecting-coal ash along the path of the blast-furnace injecting coal to the interior of the blast-furnace body.
For example, it has been proposed to improve combustibility of blast-furnace injecting coal by adding a CaO-based flux such as calcium oxide or serpentinite to pulverized coal of which the melting point of the pulverized coal ash is less than 1300° C., thereby adjusting the melting point of the ash in the pulverized coal to not less than 1300° C., and then injecting only the pulverized coal of which the melting point of the pulverized coal ash is not less than 1300° C. into the interior from the tuyere of the blast-furnace body (for example, refer to Patent Document 1 below).
Additionally, for example, a blast-furnace pulverized coal injecting operating method has been proposed, whereby permeability can be improved even in operations where the amount of injected pulverized coal is extremely large by regulating the amount of enriched oxygen or adjusting the composition, particle size, or the like of the pulverized coal to make it poorly combustible to reduce the maximum temperature reached in the raceway (for example, refer to Patent Document 2 below).